It'd be kinda cool if someone compiled a "recipe" list of vintage paints. I know you can find it for some cars where it tells you how much parts of certain colors to mix to create factory colors and you can have paint shops mix you up a batch. i think I recall even seeing a service where they'll make you the small touch up bottles.
This is the way to do it. Maaco (and presumably other body shops) will make you a bottle for ~$20.use a scanner up against any bike frame and nail the colorway....if you don't want to paint the whole bike you'll get the exact faded match (if the scanner is calibrated) but sucks if you can't find an unfaded original color..under the BB at the chainstay junction is usually least faded